Fuel injection valve for internal combustion engines

ABSTRACT

A fuel injection valve for internal combustion engines, having a valve body in which a valve member is disposed, which valve member changes into a spring plate, which is disposed in a spring chamber that receives the closing spring provided with a valve stop face on an end face. A control piston is provided defining a hydraulic control chamber, which control piston protrudes into the spring chamber, whose end face toward the combustion chamber forms a stroke stop face. As a function of pressure in the control chamber, the control piston can be moved counter to the closing force of a restoring spring from a first stroke position, remote from the valve member, toward the valve member into a second stroke position, where the control piston limits the maximum opening stroke (h) of the valve member to a partial stroke (h T ).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 35 USC 371 application of PCT/DE 00/03019 filed onSep. 2, 2000.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention is directed to fuel injection valves, and particularly tosuch a valve for internal combustion engines.

2. Brief Description of the Prior Art

One prior art fuel injection valve, known from German Published,Nonexamined Patent Application DE 196 45 900 A1 employs a pistonlikevalve member that is movable axially counter to the force of a closingspring disposed in a bore. The valve member is guided in the bore in aportion remote from the combustion chamber and, toward the combustionchamber, changes into a closing head that is guided in a slide borewhich is embodied as a blind bore. On the wall of the slide portion ofthe bore, there are a plurality of axially offset injection openings,which in the closed state of the valve member are covered by the closinghead. By the fuel pressure on the pressure shoulder disposed in thepressure chamber, the valve member is lifted from the valve seat, and asa result the pressure chamber communicates with the lower pressurechamber via a transverse bore and a middle bore embodied in the valvemember. The control edge of the closing head, in the opening strokemotion, opens the injection openings in succession, and as a result overthe increasing entire injection cross section, a shaping of the courseof injection is achieved. When the stroke stop face reaches the stopface embodied in the valve body, the opening stroke is concluded.

In such an injection valve, all the injection openings are opened in theopening stroke motion. In the partial-load range of the engine, theinjection quantity is reduced compared to full load, which in thisinjection valve means on the one hand that the injection pressure isreduced and on the other that the opening time of the injection valve isshortened. Neither of these aspects is optimal with regard to eitheroptimal atomization and distribution of the fuel in the combustionchamber or low exhaust emissions.

SUMMARY OF THE INVENTION

The fuel injection valve of the invention for internal combustionengines, has the advantage over the prior art that the opening strokecan be limited by the hydraulically controlled control piston to aportion of the maximum stroke, and as a result only some of theinjection openings, or only a partial cross section of the injectionopenings, is opened.

One embodiment of the invention has the advantage that the maximumstroke can be changed in a simple way, by replacing the relativelyreadily accessible control piston with another of a different height.

Because of the multi-part construction of the control piston in oneembodiment, easy installation of the fuel injection valve is obtained.Depending on the needs for the design of the fuel injection valve, therestoring spring can engage either the hydraulic piston or the thrustrod, which makes it possible to use the stroke stop, which according tothe invention is hydraulically variable, in various fuel injectionvalves. A further embodiment has the advantage that the injection crosssection can be reduced by providing that the injection opening is openedonly in part.

In another embodiment, the fuel injection valve has the advantage thatthe control line communicates with a high-pressure collection chambervia a control valve, so that no additional high-pressure fuel source isrequired for the control pressure in the control chamber.

In a further embodiment, it is advantageously possible to relieve thecontrol line to the fuel tank within a very brief time and thus put thecontrol piston into the first stroke position. It is accordinglypossible to change very quickly between the partial stroke and themaximum stroke of the valve member.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages and advantageous features of the subject of theinvention will be apparent from the description contained herein below,taken in conjunction with the drawings, in which:

FIG. 1 shows a longitudinal section through the fuel injection valve;

FIG. 2 is an enlarged view of the fuel injection valve of FIG. 1 in theregion of the injection openings; and

FIG. 3 shows the schematic layout of the supply to the fuel injectionvalve, with high fuel pressure and control pressure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings in detail, in FIGS. 1 and 2, a fuelinjection valve for internal combustion engines, in particularself-igniting internal combustion engines, is shown. First, the basicconstruction of the fuel injection valve will be described inconjunction with FIGS. 1 and 2, where FIG. 2 shows an enlarged detail ofFIG. 1, and then the mode of operation of the fuel injection valve willbe described.

The fuel injection valve has a multi-part valve body 1. A valve basebody 7 disposed toward the combustion chamber, toward the bottom in FIG.1, is braced with a lock nut 4 against a valve holding body 8 with theinterposition of a lower shim 14. Toward the opposite side, remote fromthe combustion chamber, of the valve holding body 8, a valve connectionbody 5 is braced with a lock nut 6, with the interposition of a valvecontrol body 2 and an upper shim 3.

In the valve base body 7, there is a bore 11 embodied as a blind bore,which narrows toward the combustion chamber and which on the end towardthe combustion chamber changes over into a slide portion 111. In thebore 11, a pistonlike, axially movable valve member 10 is disposed,which with an upper portion 101, remote from the combustion chamber, isguided in the bore 11 and which tapers toward the combustion chamber,forming a pressure shoulder 24 that is disposed in a pressure chamber 23surrounding the valve member 10.

The middle portion 102 of the valve member 10, adjoining the upperportion 101 toward the combustion chamber, narrows further toward thecombustion chamber and changes into a lower portion 103. At thetransition from the middle portion 102 to the lower portion 103 of thevalve member 10, a valve sealing face 25 is formed, which cooperateswith a valve seat 26 that is formed by a cross-sectional reduction ofthe bore 11 toward the combustion chamber.

The lower portion 103 of the valve member 10 changes, toward thecombustion chamber, into a closing head 13 that forms the end of thevalve member 10. The closing head 13 is guided sealingly in the slideportion 111 of the bore 11 the form of a blind bore and defines a lowerpressure chamber 20 formed by the bore 11. FIG. 2 shows an enlarged viewof the fuel injection valve in the region of the closing head 13.

Between the lower portion 103 of the valve member 10 and the slideportion 111 of the bore 11, an annular conduit 28 is formed, whichsurrounds the valve member 10 over its entire circumference. In thelower portion 103 of the valve member 10, at least one transverse bore22 is formed in the radial direction, and a middle bore 21 is embodied,beginning at the transverse bore 22 and extending through the end of theclosing head 13 toward the combustion chamber, coaxially to thelongitudinal axis 38 of the valve member 10. The transverse bore 22 andthe middle 21 are embodied such that they intersect in the valve member10 and thus establish a communication between the lower pressure chamber20 and the annular conduit 28. On the end of the closing head 13 towardthe combustion chamber, a control edge 29 is formed. Two axially offsetinjection openings 16, 17 are embodied in the wall of the slide portion111 of the bore 11. These openings are covered in the closed state ofthe fuel injection valve by the closing head 13, so that the injectionopenings 16, 17 communicate neither with the lower pressure chamber 20nor with the annular conduit 28. When the fuel injection valve isclosed, the annular conduit 28 and the lower pressure chamber 20 areseparated from the pressure chamber 23 by the valve sealing face 25contacting the valve seat 26.

The bore 11 is adjoined, on the end remote from the combustion chamber,by a spring chamber 36 formed in the valve holding body 8; in thischamber, by means of a cross-sectional reduction, a spring support 40 isembodied, which divides the spring chamber 36 into a lower springchamber 361 and an upper spring chamber 362. The upper portion 101 ofthe valve member 10 merges, on the end remote from the combustionchamber, with a smaller-diameter intermediate pin 41, which protrudesthrough a central bore 32, embodied in the lower shim 14, as far as theinside of the lower spring chamber 361. The intermediate pin 41 isconnected to a spring plate 30 disposed in the lower spring chamber 361,and a valve stop face 18 is embodied on the face end of this springplate remote from the combustion chamber. The transition from the valvemember 10 to the intermediate pin 41 forms a stop shoulder 19, and thetransition from the bore 11 to the smaller-diameter central bore 32 ofthe shim 14 forms a stroke stop 15 by means of the shim 14. The axialspacing of the stop shoulder 19 from the stroke stop 15, in the closedstate of the valve member 10, defines the maximum opening stroke h.Between the spring plate 30 and the spring support 40, a closing spring33 is disposed with initial tension, preferably being embodied as ahelical compression spring. It presses the spring plate 30 and thus, viathe intermediate pin 41, the valve member 10 with the valve sealing face25 against the valve seat 26.

In the valve control body 2, coaxially with the longitudinal axis 38 ofthe valve member 10, a guide bore 57 is formed, which communicates withthe upper spring chamber 362 via a central bore 64 embodied in the uppershim 3. A control piston 43 is disposed in the guide bore 57 and in thespring chamber 36 and essentially comprises two parts: a hydraulicpiston 46, which is guided in the guide bore 57, and a thrust rod 49,which is connected to the hydraulic piston 46 and from there protrudesthrough the upper spring chamber 362 into the inside of the lower springchamber 361. The thrust rod 49 is guided in the spring support 40, andits face end toward the combustion chamber is embodied as a stroke stopface 44. A spring plate 51 is disposed on the thrust rod 49 in the upperspring chamber 362, and between this plate and the spring support 40, arestoring spring 53 is disposed in a prestressed manner; the restoringspring 53 surrounds the thrust rod 49 and is preferably embodied as ahelical compression spring. The valve connection body 5, guide bore 57and hydraulic piston 46 define a control chamber 56, which can be filledwith high pressure fuel and which communicates with a control line,(FIG. 3) via a control inlet conduit 60 embodied in the valve connectionbody 5 and via a control inlet line 62. The transition from the guidebore 57 to the smaller-diameter central bore 64 of the upper shim 3forms a control piston stop 58. A high-pressure fuel connection 78 isdisposed in the valve connection body 5, and a high-pressure inlet line66 discharges into the fuel injection valve at this connection 78. Thehigh-pressure fuel connection 78 communicates with the pressure chamber23 via an inlet conduit 27 extending in the valve connection body 5, thevalve control body 2, the upper shim 3, the valve holding body 8, thelower shim 14, and the valve base body 7.

In FIG. 3, the fuel supply system for supplying high fuel pressure tothe fuel injection valves of an internal combustion engine is shownschematically. From a fuel tank 80, fuel is delivered to a high-pressurefuel pump 82 via a low-pressure line 86. From this pump, the fuel ispumped at high pressure via a high-pressure line into a high-pressurecollection chamber 68, where a largely constant high pressure ismaintained. From the high-pressure collection chamber 68, onehigh-pressure inlet line 66 leads to each fuel injection valve; thehigh-pressure inlet line supplies the pressure chamber 23 with fuel viaa fuel metering valve 88 and the inlet conduit 27 extending within thefuel injection valve. The fuel metering valve 88 opens and closes thecommunication from the high-pressure inlet line 66 to the inlet conduit27 and controls the injection event by way of the instant and durationof opening. The control inlet line 62, communicating with the controlchamber 56 via the control inlet conduit 60, of all the fuel injectionvalves is connected to a control line 70, which can be made tocommunicate with the high-pressure collection chamber 68 via a controlvalve 73. If the control line 70 is filled with fuel at high pressurevia the high-pressure collection chamber 68, then a relief of the fuelpressure into the fuel tank 80 can take place via a relief valve 76. Viathe control unit 90, not only can the individual components of the fuelinjection system be controlled, but the operating state can also bedetected, via various sensors not shown in the drawing.

The mode of operation of the hydraulically adjustable stroke stop is asfollows:

If a fuel pressure whose resultant force on the hydraulic piston 46 isgreater than the force of the restoring spring 53 prevails in thecontrol chamber 56, then the hydraulic piston 46 and thus the entirecontrol piston 43 moves, beginning from a first, upper stroke position,in which the hydraulic piston 46 rests on the valve connection body 5,toward the valve member 10 into a second, lower stroke position, untilthe hydraulic piston 46 rests on the control piston stop 58. As a resultof this motion, the stroke stop face 44 of the thrust rod 49 is alsodisplaced toward the valve member 10 and thus decreases the axialspacing of the stroke stop face 44 from the valve stop face 18 of thevalve member 10. In the lower stroke position of the control piston 43and in the closed state of the valve member 10, the axial spacing of thestroke stop face 44 from the valve stop face 18 is equal to the partialstroke hT, which is less than the maximum opening stroke h that isdefined by the axial spacing between the stop shoulder 19 of the valvemember 10 and the stroke stop 15. If the fuel pressure in the controlchamber 56 is reduced so far that the resultant force on the hydraulicpiston 46 is less than the force of the restoring spring 53, then by theforce of the restoring spring 53, the thrust rod 49 and thus also thehydraulic piston 46 moves in the direction of the valve connection body5, until the hydraulic piston 46, after traversing the control stroke hscomes to rest on the valve connection body 5. As a result, the strokestop face 44 of the thrust rod 49 also moves away from the valve member10. The control stroke hs is dimensioned such that the axial spacing ofthe stroke stop face 44 from the valve stop face 18, in this upperstroke position of the control piston 43, is greater than the maximumopening stroke h.

The mode of operation of the fuel injection valve is as follows:

If the fuel metering valve 88 is opened, the pressure in thehigh-pressure collection chamber 68 is propagated through the inletconduit 27 as far as the pressure chamber 23. The resultant force in theaxial direction on the pressure shoulder 24 thus increases, until thisforce is greater than the force of the closing spring 33. With the valvesealing face 25, the valve member 10 lifts away from the valve seat 26,and as a result the pressure chamber 23 communicates with the annularconduit 28 and thus also, via the transverse bore 22 and the middle bore21, communicates with the lower pressure chamber 20. As soon as thecontrol edge 29 reaches the injection opening 17, fuel is injected viathe injection opening 17 into the combustion chamber. The further courseof the opening stroke motion depends on the stroke position of thecontrol piston 43: If the control piston 43 is in the first, upperstroke position, then the valve member 10 executes the maximum openingstroke h, until, with its stop shoulder 19, it comes into contact withthe stroke stop 15; the shim 14 forms the stroke stop 15 disposedrigidly in the valve body 1. In the course of the opening stroke motionof the valve member 10, the control edge 29 first opens the injectionopening 17 toward the combustion chamber and then the injection opening16 offset from it and remote from the combustion chamber. The injectionaccordingly takes place first through the injection opening 17 and thenthrough both injection openings 16, 17 jointly. the closing motion ofthe valve member 10 takes place whenever the pressure in the pressurechamber 23 drops far enough that the resultant force on the valve member10 at the pressure shoulder 24, the valve sealing face 25 and the faceend, toward the combustion chamber, of the valve member 10 in the lowerpressure chamber 20 becomes less than the force of the closing spring33. The valve member 10 is moved by the closing spring 33 in thedirection toward the combustion chamber, until the valve sealing face 25comes to rest on the valve seat 26. This disconnects the pressurechamber 23 from the lower pressure chamber 20, and the closing head 13closes the injection openings 16, 17.

If conversely the control piston 43 is in the lower stroke position,then the valve member 10 in its opening stroke motion, after traversingthe partial stroke h_(T), comes to rest with the stroke stop face 44 onthe valve stop face 18. The partial stroke h_(T) is dimensioned suchthat the control edge 29 of the closing head 13, at the end of thepartial stroke motion, rests between the injection openings 16 and 17,so that only the injection opening 17 nearer the combustion chambercommunicates with the pressure chamber 23, and only through theinjection opening 17 is fuel injected into the combustion chamber. Thestop of the valve member 10 on the control piston 43 is hydraulicallydamped by the control chamber 56. The closing motion of the valve member10 is initiated in the same way as the closing motion after theexecution of the maximum opening stroke h.

The control of the control piston 43 is effected via the pressure in thecontrol line 70. Since a largely constant high fuel pressure alwaysprevails in the high-pressure collection chamber 68, the fuel pressurein the control line 70 can be raised up to the pressure in thehigh-pressure collection chamber 68 at any time by opening the controlvalve 73. As a result, the control piston 43 moves as described abovefrom the first, upper stroke position to the second, lower strokeposition, and the opening stroke of the valve member 10 is limited to apartial stroke h, of the maximum opening stroke h. The partial strokeh_(T) amounts to from 40 to 60%, and preferably approximately 50%, ofthe maximum opening stroke h. The relief of the control line 70 takesplace into the fuel tank 80, via the relief valve 76. It is thuspossible, within only a few injection cycles, to reduce the pressure inthe control line 70 and thus to move the control piston 43 from thesecond, lower stroke position to the first, upper stroke position, as aresult of which the valve member 10 can again execute the maximumopening stroke h. Because of the available high-pressure collectionchamber 68, it is accordingly unnecessary to have a separatehigh-pressure fuel source for the control line 70.

As an alternative to the fuel injection valve described above, it canalso be provided that the maximum opening stroke of the valve member 10in the first, upper stroke position of the control piston 43 is definedby the axial spacing of the stroke stop face 44 from the valve stop face18. The control stroke hs and the injection openings 16, 17 are embodiedin this case such that at the maximum opening stroke of the valve member10, both injection openings are opened. In the first, upper strokeposition of the control piston 43, the valve member 10 comes to rest onthe control piston as a stop, so that the stroke stop 15 can be omitted.

In a further alternative embodiment of the fuel injection valvedescribed above, it is provided that the thrust rod 49 of the controlpiston 43 is omitted, and instead, the valve member 10 protrudes pastthe spring plate 30 to the inside of the upper spring chamber 362. Theend face of the valve member 10 toward the hydraulic piston is embodiedin this case as a valve stop face 18, which in the second, lower strokeposition of the hydraulic piston 46 comes to rest, in the opening strokemotion, directly on the hydraulic piston 46. In this embodiment, therestoring spring 53 is braced between the spring support 40 and thehydraulic piston 46.

In still another alternative embodiment of the above-described fuelinjection valve, it is provided that instead of a plurality of axiallyoffset injection openings, only one or more injection openings 16, 17embodied at the same height are embodied in the slide portion 111 of thebore 11. The maximum opening stroke h and the partial stroke h_(T) aredimensioned in this case such that the injection opening is opened onlypartially by the control edge 29 in the partial stroke h_(T), and as aresult a further reduction in the entire injection cross section isobtained. The full cross section of the injection opening is opened whenthe maximum opening stroke h has been executed.

The foregoing relates to preferred exemplary embodiments of theinvention, it being understood that other variants and embodimentsthereof are possible within the spirit and scope of the invention, thelatter being defined by the appended claims.

What is claimed is:
 1. In a fuel injection valve for internal combustionengines, having a valve body (1), in which a bore (11) formed as a blindbore is embodied so that toward a combustion chamber it changes into aslide portion or bore (111), on a wall of which at least one injectionopening (16, 17) is disposed, and having a pistonlike valve member (10),which is guided in a region of the bore (11) remote from the combustionchamber and is axially movable counter to the force of at least oneclosing spring (33) and which on its end toward the combustion chamberchanges into a closing head (13) that is guided in the slide portion orbore (111) of the bore (11) and that closes the injection opening (16,17), the injection opening (16, 17) being openable entirely or in partby an inward-oriented opening stroke motion of the valve member (10), asa result of which an injection cross section changes as a function of anopening stroke of the valve member (10), which valve member (10), forlimiting its opening stroke motion to a maximum opening stroke (h) comesto rest on a stop, and on which valve member a pressure shoulder (24)acting in an opening direction is embodied, the improvement comprising,in a region of the valve body (1) remote from the combustion chamber, acontrol piston (43) is disposed at least approximately coaxially to thevalve member (10), the control piston being guided axially movably in acontrol bore (57) embodied in the valve body (1) and defining a controlchamber (56), and fuel under pressure can be delivered to the controlchamber (56), by means of which the control piston (43) can be moved,counter to a force of a restoring spring (53), from a first strokeposition toward the valve member (10) into a second stroke position, asa result of which the control piston (43) acts as a stop (44) for thevalve member (10) and limits the opening stroke motion of the valvemember (10) to a partial stroke (h_(T)) that is less than the maximumstroke (h).
 2. The fuel injection valve of claim 1, wherein the maximumstroke (h) of the valve member (10) in the first stroke position of thecontrol piston (43) is formed by a stroke stop (15) embodied rigidly onthe valve body (1).
 3. The fuel injection valve of claim 1, wherein thecontrol piston (43), in its second stroke position, acts as a stop forthe valve member (10) to limit the opening stroke motion of the valvemember to the partial stroke (h_(T)).
 4. The fuel injection valve ofclaim 1, wherein the control piston (43) is embodied in two parts, and afirst part forms a hydraulic piston (46) and defines the control chamber(56), and a second part, which is connected to the hydraulic piston(46), is embodied as a thrust rod (49), which acts as the stop (44) forthe valve member (10).
 5. The fuel injection valve of claim 4, whereinthe restoring spring (53) is braced on the hydraulic piston (46).
 6. Thefuel injection valve of claim 4, wherein the restoring spring (53) isbraced on the thrust rod (49).
 7. The fuel injection valve of claim 1,wherein the control piston (43), in its second stroke position, definesthe opening stroke of the valve member (10) to the partial stroke(h_(T)) that amounts to approximately 40-60% of the maximum openingstroke (h), and preferably approximately 50%.
 8. The fuel injectionvalve of claim 1, wherein in the wall of the slide bore (111), at leasttwo injection openings (16, 17) are embodied, axially offset from oneanother.
 9. The fuel injection valve of claim 8, wherein in thelimitation of the opening stroke of the valve member (10) to the partialstroke (h_(T)), only one injection opening (17) is opened.
 10. The fuelinjection valve of claim 8, wherein the closing head (13) at the maximumopening stroke (h) of the valve member (10) opens both injectionopenings (16, 17) one after the other in the course of the openingstroke motion.
 11. The fuel injection valve of claim 1, wherein theclosing head (13), upon a limitation of the opening stroke to thepartial stroke (h_(T)) in the opening stroke motion of the valve member(10), opens the at least one injection opening (16, 17) only partially.12. The fuel injection valve of claim 1, wherein the fuel injectionvalve communicates via a high-pressure inlet line (66) with ahigh-pressure collection chamber (68).
 13. The fuel injection valve ofclaim 12, wherein the control chamber (56) communicates, via an inletbore (60) embodied in the valve body (1) and via a fuel inlet valve(62), with a control line (70) that communicates with the high-pressurecollection chamber (68) via a control valve (73).
 14. The fuel injectionvalve of claim 13, wherein the control line (70) can be relieved to afuel tank (80) via a relief valve (76).